1. Field of the Invention
The present invention relates to a sound mixing equipment, more particularly a sound mixing equipment, which is provided with a manually activated control constructed such that it is not subject to wear that is prone to occur on conventional manually activated controls having variable resistors.
2. Brief Description of the Prior Art
In order to help increase hot and exciting atmosphere in a concert or a party such as is held in a PUB or a dancing hall, the DJ would produce special sound effects by mixing input sound signals into output sound signals with a sound mixing equipment which includes separate manually activated controls for each sound input signal. The sound input signals may include signals from several musical instruments and voices. The sound output signals may be provided to speakers.
Referring to FIG. 4, a conventional sound mixing equipment 5 includes an attenuation circuit 51, and a stereophonic sound mixing circuit 52. The attenuation circuit 51 includes resistors 511, 512, 513, and 514. The stereophonic sound mixing circuit 52 includes resistors 521, 522, 523, and 524, and amplifiers 525, and 526. A first channel, and a second channel are connected to musical instruments or record players. The first channel has a right channel, and a left channel connected to the resistor 513, and the resistor 511 respectively. The second channel has a right channel, and a left channel connected to the resistor 514, and the resistor 512 respectively. The attenuation circuit 51 is connected to a first variable resistor 515 disposed between the resistors 511 and 512, and to a second variable resistor 516 disposed between the resistors 513 and 514 so that it in parallel with the variable resistors 515 and 516. Then, the resistors 511, 512, 513, and 514 are connected to the resistors 521, 522, 523, and 524 of the stereophonic sound mixing circuit 52 respectively. And, the resistors 521, 522, 523, and 524 plus adjustable conducting legs of the variable resistors 515 and 516 are connected to corresponding conducting legs of the amplifiers 525, and 526. Manually operated controls (not shown) are joined to the adjustable conducting legs of the variable resistors 515 and 516.
In using the sound mixing equipment, referring to FIGS. 4, and 5, the users move the manually operated controls to adjust resistance at each section of the variable resistors 515, 516. When resistances at both sections of each of the variable resistors are equal, the input sound signals are mixed into output sound signals in which signals from the first channel and those from the second channel are of equal volume. When resistance at one section of the variable resistor 515 or 516 is bigger than resistance at the other section, there will be bigger volume of sound signals from the channel connected to the latter section in the output sound signals. When resistance at one section of the variable resistor 515 or 516 is zero, and resistance at the other section equals entire resistance of the resistor, there will be no sound signals from the channel connected to the latter section in the output sound signals.
However, this sound mixing equipment is found to have a disadvantage that the variable resistors are subject to oxidation at contacts. And, wear and loss of elasticity are prone to occur on the variable resistors because the adjustable conducting legs of the variable resistors are moved relative the other portions frequently in operating the sound mixing equipment. Consequently, the electrical contact becomes loose.